Infinitely Polar Bear has made its debut at this year's Sundance Film Festival and seems to have emerged as one of the most prominent movies, despite some unsure reviews. In the film Mark Ruffalo ('The Avengers') plays Cameron, a dysfunctional father grappling with bipolar disorder who tries to win back his wife Maggie (Zoe Saldana) by attempting to take responsibility over their two daughters. The film is loosely based on the childhood experiences of writer and director Maya Forbes, whose father called his condition Infinitely Polar Bear.

Mark Ruffalo
Mark Ruffalo Searches For The Humour In Bipolar Disorder In 'Infinitely Polar Bear.'

Despite the fairly serious subject of mental health, the dramedy manages to inject some humour into the family's trying situation. Premiering at Sundance, the movie received a standing ovation at the weekend and everyone seems to be talking about the wider release of the sweet and poignant film. Both lead actors may be known for playing superheroes in action movies but Saldana has said that she enjoyed playing a parent with Ruffalo because "those are the real avengers, the real guardians of the galaxy!" via NY Daily News.

Zoe Saldana
Zoe Saldana Shines As The Star Of The 'Infinitely Polar Bear' Show, Say Critics.

The heavy weight Hollywood actors behind a low-budget indie may be why Infinitely Polar Bear has received such attention since its screening. Described as "an epic tale of familial dysfunction" by The Guardian, as well as a "remarkable story," the movie seems to fall flat trying to find the cute element of a destructive mental disorder. "As a drama it's unbalanced, trying too hard to be lovable," says Henry Barnes, who finds Ruffalo the wrong actor for the job: "We're shown a little of [Cameron's] depression and a lot of the mania, which is played for laughs."

Barnes weighs up "Infinitely Polar Bear is heartfelt and honest, but it's too cute by half." Similarly The Wrap picks up on Ruffalo being a bad fit, praising the rest of the "down to Earth" cast for "anchoring the film," but lamenting that "this usually reliable actor goes too big, and it sucks the oxygen out of the rest of the movie."

Mark Ruffalo Premiere
The Usually Loveable Ruffalo's Performance Grated On Some Critics This Time.

Again Total Film heaps praise on Saldana in the "sweet, warm, funny" comedy but says that Ruffalo's performance "tips a little too far into manic quirk overdrive." Matt Risley compliments Forbes' "impressive" directorial debut as "vibrant and warm-hearted," praising the "instantly adorable and endlessly amusing" daughters and a "fun" yet "infuriating" Ruffalo. However, it seems that Saldana is the star of the show here, praised for "offering dramatic shades hereto unseen as the matriarch torn between her children, her husband and her work."

The Wrap's Alonso Duralde sums up Infinitely Polar Bear's main issue pretty well: "audiences that love or hate "Infinitely Polar Bear" will be divided precisely by how they feel about Ruffalo."